The present invention relates to a new and improved construction of mold for fabricating articles or the like --hereinafter simply conveniently referred to as articles-- from a fluent or flowable material, especially rubber, and which mold is of the type comprising two mold parts or components enclosing a mold compartment or cavity, one of the mold parts possessing at the region of the mold separation or parting plane a tear or break groove surrounding the mold compartment.
During the fabrication of articles from fluent materials, especially rubber, a greater amount of material must be supplied into the mold than needed for the production of the article in order to insure that the mold compartment will be always completely filled with the molding material without the inclusion of air. During venting of the mold the air inclusions escape out of the mold compartment and thus also excess material into the so-called break or tear groove or overflow groove which is always needed. The transition between the mold compartment and the tear groove should be as thin as possible in order to insure that following removal of the fabricated article from the mold the material which has collected in the tear or overflow groove can be easily removed from the article.
It is generally conventional practice to arrange the tear or break groove in the same mold part or component where there is at least predominantly also arranged the mold compartment. The tear groove normally has a triangular cross-sectional configuration, and hence, its inner wall forms an obtuse angle with respect to the mold parting or separation plane, i.e., an angle exceeding 90.degree.. Owing to this configuration the marginal rim or outer edge of the mold compartment is surrounded by an acute-angle converging collar. The apex or tip of this collar is extremely susceptible to damage. Such damage, which for instance can appear in the form of notches or indentations at the tip of the collar, is however extremely undesirable since it increases the thickness of the connection to the material in the tear groove and either renders difficult or impossible a uniform tearing or breaking-out of the ring of material collected in the tear or break groove. It is for this reason that a special working step is needed for tearing away the material in the tear groove, requiring the services of additional personnel.
With the heretofore known molds the molding material, after filling the tear groove of triangular cross-sectional configuration, can flow between both of the mold parts or components and thus vulcanize up to a thickness of 1 millimeter or more. Separation of the excess material from the actual molded article is then no longer possible without resorting to the aid of auxiliary means. Additionally, the escaping material is of varying thickness depending upon the temperature of the mold and the flow properties of the molded material. This requires a comparatively large proportion of excess material and thus material losses. Moreover, since the material does not flow out uniformly to all sides it should be apparent that at the parting plane of the mold there are formed at different locations different material thicknesses, resulting in canting of the mold parts with respect to one another. The large forces which are thus effective can bend the guide pins, dowels or guide sleeves or the like of the mold parts or damage the same, resulting in inaccurate centering of the mold parts relative to one another, so that the guide pins- or sleeves oftentimes must be replaced.